1. Technical Field
The present invention relates to a piezoelectric element, a method of forming a piezoelectric element, and an ultrasonic device.
2. Related Art
A piezoelectric body which is deformed when a voltage is applied thereto is widely used. Two or more electrodes are installed on the piezoelectric body. If a voltage is applied between the electrodes, the piezoelectric body is deformed. In addition, when the piezoelectric body is deformed, a voltage difference occurs between two electrodes. It is possible to generate ultrasonic waves using properties of the piezoelectric body. In addition, it is possible to detect ultrasonic waves by analyzing a change in voltage difference between the electrodes when the piezoelectric body receives the ultrasonic waves and vibrates.
International Publication No. 2014-050235 discloses a piezoelectric element in which electrodes are installed on a piezoelectric body. The piezoelectric body has a plate shape, and a front surface and a rear surface are parallel to each other. A first electrode is installed on the front surface, and a second electrode is installed on the rear surface. The planar shape of the piezoelectric body is a rectangular shape, and includes four sides. One side of the four sides is assumed to be a first side.
The first electrode is connected to a first terminal on the rear surface via a first wiring passing through the first side. The second electrode is connected to a second terminal on the front surface via a second wiring passing through the first side. The first wiring and the second wiring are disposed along the first side. The piezoelectric element is mounted on a substrate, and a third terminal and a fourth terminal are installed on the substrate. The first terminal is connected to the third terminal, and the second terminal is connected to the fourth terminal.
In the piezoelectric element disclosed in International Publication No. 2014-050235, the first wiring and the second wiring are installed along one side. A method of patterning a piezoelectric body via a photolithographic method, and performing etching is effective in disposing a very small piezoelectric element on a substrate. When a resist is disposed on a piezoelectric body, and patterning and etching are performed, chemical reactions occur between etching gas, the resist, and the piezoelectric body. A compound is formed due to the chemical reactions. If the piezoelectric body has a rectangular shape, a compound is formed along each of four sides. Side surfaces of the piezoelectric body become substantially perpendicular to an upper surface of the piezoelectric body due to the compound. It is possible to limit a side surface, on which the compound is formed, to one side surface by spraying a chemical solution to the compound. That is, if the piezoelectric body includes four side surfaces, it is possible to allow the formation of the compound on only one surface. The compound is also referred to as a fence.
Wirings are installed from the upper surface of the piezoelectric body to the substrate. In this case, after a metallic film and a resist are installed and patterning is performed, etching is performed. In this case, a residual of the metallic film remains on a substantially perpendicular side surface. If two or more wirings are installed in a location where a residual of the metallic film is present, the wirings are short-circuited to each other, and the piezoelectric element malfunctions. Desirably, in the piezoelectric element, it is possible to prevent a short circuit between the first wiring and the second wiring which are installed in the piezoelectric body, which is caused by a residual of the metallic film.